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Subject: fs: dcache: Use cpu_chill() in trylock loops
From: Thomas Gleixner <tglx@linutronix.de>
Date: Wed, 07 Mar 2012 21:00:34 +0100
Retry loops on RT might loop forever when the modifying side was
preempted. Use cpu_chill() instead of cpu_relax() to let the system
make progress.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
fs/autofs4/autofs_i.h | 1 +
fs/autofs4/expire.c | 2 +-
fs/dcache.c | 5 +++--
fs/namespace.c | 3 ++-
4 files changed, 7 insertions(+), 4 deletions(-)
--- a/fs/autofs4/autofs_i.h
+++ b/fs/autofs4/autofs_i.h
@@ -34,6 +34,7 @@
#include <linux/sched.h>
#include <linux/mount.h>
#include <linux/namei.h>
+#include <linux/delay.h>
#include <asm/current.h>
#include <asm/uaccess.h>
--- a/fs/autofs4/expire.c
+++ b/fs/autofs4/expire.c
@@ -150,7 +150,7 @@ static struct dentry *get_next_positive_
parent = p->d_parent;
if (!spin_trylock(&parent->d_lock)) {
spin_unlock(&p->d_lock);
- cpu_relax();
+ cpu_chill();
goto relock;
}
spin_unlock(&p->d_lock);
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -19,6 +19,7 @@
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/fsnotify.h>
+#include <linux/delay.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/hash.h>
@@ -589,7 +590,7 @@ static struct dentry *dentry_kill(struct
failed:
spin_unlock(&dentry->d_lock);
- cpu_relax();
+ cpu_chill();
return dentry; /* try again with same dentry */
}
@@ -2398,7 +2399,7 @@ void d_delete(struct dentry * dentry)
if (dentry->d_lockref.count == 1) {
if (!spin_trylock(&inode->i_lock)) {
spin_unlock(&dentry->d_lock);
- cpu_relax();
+ cpu_chill();
goto again;
}
dentry->d_flags &= ~DCACHE_CANT_MOUNT;
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -14,6 +14,7 @@
#include <linux/mnt_namespace.h>
#include <linux/user_namespace.h>
#include <linux/namei.h>
+#include <linux/delay.h>
#include <linux/security.h>
#include <linux/idr.h>
#include <linux/init.h> /* init_rootfs */
@@ -355,7 +356,7 @@ int __mnt_want_write(struct vfsmount *m)
smp_mb();
while (ACCESS_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) {
preempt_enable();
- cpu_relax();
+ cpu_chill();
preempt_disable();
}
/*
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